Laser-recrystallized polycrystalline-silicon thin-film transistors with low leakage current and high switching ratio

Abstract

Laser-recrystallized polycrystalline-silicon thin-film transistors (poly-Si TFT's) with offset-gate structures have been fabricated on quartz substrates. Offset-gate structures make it possible to reduce leakage currents to as low as 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-14</sup> A/µm at V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</inf> = 10 V, more than two orders of magnitude lower than that in conventional-structure poly-Si TFT's. Optimization of the dopant concentration in offset-gate regions minimizes degradation of drive current, enabling high switching ratios exceeding 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> . Calculations based on the quasi-two-dimensional model indicate that the reduction in leakage current is due to a decrease in lateral electric field strength in the drain depletion region.